EP1590813B1 - Method for making a closed contained and said closed container. - Google Patents

Abstract

A container, comprising a basically cylindrical or prismatic metal body (1) open at the top (11), and a lid (2) with a rim (23) that matches the shape of the container top, is closed and sealed in a hostile atmosphere by a remotely controlled automated device. The lid is fitted to the top of the body with the aid of an inner guide ring (3) so that their adjoining edges are in contact, and they are then joined and sealed by a continuous penetrative weld while pressure is applied to one of the components, preferably the lid. The weld is formed by a plasma jet, preferably without additional metal, and the guide ring has a groove and de-gassing duct to release excess pressure inside the container.

Description

• un procédé d'élaboration d'un conteneur fermé, dont la fermeture est étanche et résistante mécaniquement, par solidarisation de deux éléments métalliques du type :
  1. a) corps de forme essentiellement cylindrique ou prismatique, présentant un fond, une(des) paroi(s) axiale(s) et ouvert en son extrémité axiale supérieure,
  2. b) couvercle, de forme plus ou moins complexe, présentant une(des) paroi(s), destinée(s) à être disposée(s), en l'extrémité axiale supérieure dudit corps, en regard de la(des) paroi(s) axiale(s) dudit corps, dans le prolongement de celle(s)-ci ; procédé mis en oeuvre dans des conditions particulières, difficiles ;
• ledit conteneur fermé, dont la fermeture est étanche et résistante mécaniquement, dont la structure comprend, solidarisés l'un à l'autre, les deux éléments métalliques identifiés ci-dessus (corps, couvercle) ;
• les éléments constitutifs dudit conteneur, considérés indépendamment et conjointement, avant leur solidarisation :
  1. a) ledit corps ;
  2. b) ledit couvercle ; la structure interne de l'un desdits deux éléments comportant un guide d'accostage ; ainsi que
  3. c) ledit guide d'accostage, per se, lorsqu'il intervient à titre de pièce rapportée.

The present invention relates to the development of a closed container according to the preamble of claim 1, and said closed container according to claim 10, the present invention more specifically for objects:

• a method of producing a closed container, the closure of which is sealed and mechanically resistant, by joining two metal elements of the type:
  1. a) essentially cylindrical or prismatic shaped body, having a bottom, one (or more) axial wall (s) and open at its upper axial end,
  2. b) lid, of more or less complex shape, having a wall (s), intended (s) to be arranged (s), at the upper axial end of said body, facing the (the) wall (s) ( s) axial (s) of said body, in continuation of that (s); process implemented under particular, difficult conditions;
• said closed container, the closure is sealed and mechanically resistant, the structure comprises, secured to one another, the two metal elements identified above (body, lid);
• the constituent elements of said container, considered independently and jointly, before joining them together:
  1. a) said body;
  2. b) said lid; the internal structure of one of said two elements comprising a docking guide; as well as
  3. (c) the docking guide, per se, when acting as an insert.

The present invention has been developed in the context of conditioning and storage of nuclear waste. It is however not limited to this context

The patent US5,346,096 discloses containers which are not containers of the type of those of the present invention (body + cover), which are not obtained by joining (welding) within the meaning of the invention (see below) a cover to a body. The container according to US5,346,096 includes a cast iron body. On said cast iron body, it is welded, by alumino-thermie, a steel ring. Two pieces complementary, constituting a lid, are arranged inside this ring. Welding, ring on body, is a welding of manufacture which does not follow a direct docking ...

The present invention is more generally in the context of the packaging, presumably in view, of the storage of hazardous waste, handled remotely. The body of a container, charged with said hazardous waste (for example of the nuclear waste compacted in wafers), open at its upper axial end (and not only in a small diameter orifice) is to be sealed with a cover. The closure in question must be watertight (because of the dangerousness of said waste) and mechanically resistant (it is desired, subsequently, to handle the loaded container closed by its cover). It must also be able to be implemented in a hostile environment (nuclear, in particular), automatically, with remote control.

In the context of packaging bulk nuclear waste in containers, said waste being bound by a binder of the glass or cement type, the filling orifices of said containers (small diameter orifices) are closed by placing and welding a sheet on those -this. The diameter of said filling orifices is not substantial and a significant mechanical strength of the weld in question is not necessarily required while the sealing of said weld is an indispensable feature. The sealing technique implemented in this context (less severe specifications) was not directly transferable in the context of the invention (where the specifications are particularly severe). It is intended to seal a substantial surface and the closure in question must be mechanically resistant.

In said context of the invention, it was first envisaged the implementation of a conventional mechanical closure method, with joint intervention of flange-type parts, bolts, joints. Such a method involves many manipulations and it inevitably raises the problem of aging of the seal (s) in question.

It was then conceived the method of the invention, which typically comprises two steps: a first step of docking the two metal elements to be welded and a second welding step, implemented under particular conditions.

1. a) corps de forme essentiellement cylindrique ou prismatique, présentant un fond, une(des) paroi(s) axiale(s) et ouvert en son extrémité axiale supérieure ;
2. b) couvercle, de forme plus ou moins complexe, présentant une(des) paroi(s), destinée(s) à être disposée(s), en l'extrémité axiale supérieure dudit corps, en regard de la(des) paroi(s) axiale(s) dudit corps, dans le prolongement de celle(s)-ci.

According to its first object, the present invention thus relates to a method of producing a closed container, whose closure is sealed and mechanically resistant, by joining two metal elements of the type:

1. a) substantially cylindrical or prismatic shaped body, having a bottom, one (or) wall (s) axial (s) and open at its upper axial end;
2. b) lid, of more or less complex shape, having a wall (s), intended (s) to be arranged (s), at the upper axial end of said body, facing the (the) wall (s) ( s) axial (s) of said body, in continuation of that (s) -ci.

The body in question, advantageously substantially cylindrical in shape, is generally loaded. It is intended to condition its loading in the closed container. The lid intervenes with its (their) wall (s) axial (s) in the extension of that (s) of said body.

• un accostage desdits deux éléments métalliques, de sorte que les extrémités de leurs parois disposées en regard soient maintenues en contact ;
• la réalisation d'une soudure, continue, pénétrée, sur tout le pourtour desdits deux éléments métalliques, au niveau de leurs extrémités de parois maintenues en contact.

Typically, the process for producing the closed container of the invention is carried out in a hostile environment, automatically, with remote control (because of the dangerous nature of the load in question) and it comprises the two successive stages below:

• a docking of said two metal elements, so that the ends of their walls arranged opposite are kept in contact;
• the realization of a weld, continuous, penetrated, all around said two metal elements, at their wall ends held in contact.

During the first of said steps, said two metal elements to be secured (body and cover) are approached and then brought into contact, edge to edge, in a stable manner.

During the second of said steps, a weld is made at the ends in contact with said two metal elements (body and cover). This weld is of a particular type. It is implemented on surfaces, maintained in contact, without overlapping. It is continuous, so that the required seal is obtained. It is penetrated, that is to say implemented over the entire thickness of the walls in question, so that the required mechanical strength is obtained.

These two successive steps of the method of the invention are likely to be implemented at the same position or at different positions.

Thus, according to a variant, there is a loaded container which is brought to a single station. At this single station, said loaded container is capped with a suitable cover and welding is performed;
according to another variant, said loaded container is capped said lid at a first station and the welding is performed at a second station. This other variant is illustrated further in the present text, in a particular context.

The approach of the two elements to be welded, during the first docking step, is advantageously a guided approach which involves a docking guide, arranged in the internal structure of one or the other of said two elements to be welded. . It is not excluded from the scope of the method of the invention that such a guided approach involves means external to the structure of said two metal elements in question (body and cover). This implies however a more complex implementation.

For the implementation of welding, it is advantageously exempted from any pointing operation. It is recommended to maintain in contact the ends of the walls of one and the other of the elements to be joined, exerting a force on one of said elements, the other being obviously kept motionless. It operates, advantageously, exerting such a force on the lid, the body being perfectly blocked.

The welding can be carried out with or without filler metal. The intervention of a filler metal a priori makes the implementation of welding easier but, in fact, complicates it in the particular context of the invention, due to operating constraints (hostile environment, remote control, ...)

Thus, according to an advantageous variant, the welding implemented during the second step of the process of the invention is free of filler metal.

The welding used, with or without filler metal, preferably without filler metal (see above), may be according to various techniques, familiar to the skilled person, and in particular according to the laser technique, or the electric arc technique with refractory electrode (plasma or "TIG" (tungsten inert gas)).

It is particularly recommended the implementation of plasma welding, jet outlet, with protection against the melt and limiting the internal overpressure. The principle of plasma jet welding (also called "keyhole") is familiar to the skilled person. In the context of the present invention, it is advantageous to use such a welding technique, with protection against the melt (generally by argon inerting, in order to avoid any oxidation) and to control overpressure. generated within the container (due to the introduction of the plasma jet into said container).

This welding technique is, very particularly preferably, implemented on a container having in its internal structure a docking guide; said docking guide intervening, in addition to the docking of the two elements to be welded, also during said welding. Said docking guide occurs, during said welding, for receiving and guiding the emerging jet. In the context of this particularly preferred variant, the emerging jet opens into a groove, equipped with at least one degassing chimney, machined in said docking guide arranged in the internal structure of the body or the lid of the container. The gas evacuated from said groove via the said degassing chimney (s) does not accumulate in the container. Indeed, it is provided in the structure of said container, at the body and / or the cover of said container, preferably at the lid, at least one degassing vent. This degassing vent is likely to be closed after completion of the welding.

• l'étape d'accostage,
• l'étape de soudage ; avec intervention du guide d'accostage lors de ces deux étapes , et
• une troisième étape d'obturation totale du conteneur obtenu par soudage de son corps et de son couvercle ; troisième étape d'obturation de l'(des) évent(s) de dégazage utile(s) lors de la mise en oeuvre de ladite étape de soudage.

In the context of this particularly preferred variant of the process of the invention, it is therefore successively implemented:

• the docking stage,
• the welding step; with intervention of the docking guide during these two stages, and
• a third step of completely sealing the container obtained by welding its body and its lid; third step shut off the vent (s) degassing (s) useful (s) during the implementation of said welding step.

• selon un axe de soudage horizontal, sur le conteneur (corps + couvercle) vertical ; et/ou
• avec le conteneur fixe et une tête de soudage mise en rotation autour dudit conteneur, au niveau des extrémités des parois, du corps et du couvercle dudit conteneur, maintenues en contact.

The welding, carried out according to any welding technique and particularly according to the open jet plasma method, is advantageously according to one and / or the other of the following variants:

• along a horizontal welding axis, on the vertical container (body + cover); and or
• with the fixed container and a welding head rotating around said container, at the ends of the walls, the body and the lid of said container, held in contact.

The method of the invention, as described above in general terms and hereinafter with reference to the appended figures, is advantageously used to develop a closed container for the conditioning and storage of hazardous waste, in particular waste nuclear (more particularly nuclear waste previously compacted into slabs).

1. a) corps de forme essentiellement cylindrique ou prismatique, présentant un fond, une(des) paroi(s) axiale(s) et ouvert en son extrémité axiale supérieure ;
2. b) couvercle, de forme plus ou moins complexe, présentant une(des) paroi(s), destinée(s) à être disposée(s), en l'extrémité axiale supérieure dudit corps, en regard de la(des) paroi(s) axiale(s) dudit corps, dans le prolongement de celle(s)-ci.

According to its second object, the present invention relates to the containers that can be obtained at the end of the implementation of the method, the first object of said invention, discussed above. Said containers have their structure which bears the signature of said method. Such containers are closed, the closure in question being waterproof and mechanically resistant. Their structure comprises, secured to one another, the two metal elements of the type, already specified above:

1. a) substantially cylindrical or prismatic shaped body, having a bottom, one (or) wall (s) axial (s) and open at its upper axial end;
2. b) lid, of more or less complex shape, having a wall (s), intended (s) to be arranged (s), at the upper axial end of said body, facing the (the) wall (s) ( s) axial (s) of said body, in continuation of that (s) -ci.

The body of said containers is advantageously substantially cylindrical in shape. It is generally loaded in the elements packaged in said container.

• la solidarisation, corps/couvercle, est de type soudure, bord à bord, avantageusement sans métal d'apport ;
• la structure interne desdits conteneurs comporte, au niveau du cordon de soudure (du plan de jonction desdits corps/couvercle) un guide d'accostage qui présente :
  • + au niveau dudit cordon de soudure, côtés parois, une gorge équipée d'au moins une cheminée de dégazage,
  • + au-dessus ou en dessous, avantageusement au-dessus, dudit cordon de soudure, côté parois, une extrémité chanfreinée ;
• le corps ou/et le couvercle, avantageusement le couvercle, desdits conteneurs, comporte(nt) au moins un évent de dégazage obturé.

Characteristically:

• the fastening, body / cover, is welding type, edge to edge, preferably without filler metal;
• the internal structure of said containers comprises, at the weld seam (of the junction plane of said body / cover), a docking guide which presents:
  • + at the level of said weld bead, side walls, a groove equipped with at least one degassing chimney,
  • + above or below, advantageously above, said weld seam, side walls, a chamfered end;
• the body or / and the lid, advantageously the lid, of said containers, comprises (s) at least one closed degassing vent.

• soit, usiné dans la masse du corps ou du couvercle dudit conteneur, avantageusement usiné dans la masse dudit corps dudit conteneur ;
• soit, à titre de pièce rapportée, soudée ponctuellement audit corps ou audit couvercle.

It is perfectly conceivable, having considered the above description of the process, the above characteristics of the containers. Their external structure comprises the weld body / cover and at least one closed degassing vent; their internal structure comprises, at the level of said weld, the docking guide. It is arranged at a suitable level so that its groove is facing the weld bead (it had to be able to receive the plasma jet, during the implementation of a plasma welding); and
so that its chamfered end participated in the berthing.
It is arranged in the internal structure of the lid or the body of the container. In fact, the docking guide comes in, usually:

• either machined in the mass of the body or the lid of said container, advantageously machined in the mass of said body of said container;
• or, as an insert, welded punctually to said body or said lid.

It is now proposed to illustrate the invention, in its process aspects and "products", in a particular context, with reference to the appended figures; this, in no way limiting, both with reference to said context as said figures.

Figures 1A, 1B, 1C schematizing steps of a nuclear waste packaging process, packaging method which includes the development of a closed container according to the invention.

Figure 2 shows, in section, such closed container of the invention, before closing the degassing vent arranged on its cover.

Figure 2A shows an enlargement of the solder area body / cover of said container of the figure 2 welding zone where, typically, the docking guide intervenes.

Figures 2B and 2C show in the same way variants of such a docking guide.

Figure 3 illustrates, in perspective, a docking guide of the invention, intended to act as an insert.

On the Figure 1A , there is shown an empty container 1 + 2 consisting of a cylindrical body 1, open at its upper axial end 1 '(visible on the Figure 1B ), and a cover 2, closing said upper axial end 1 '. Said container 1 + 2 is disposed on a transfer carriage 5, able to be translated. It is stabilized, on said carriage 5, thanks to the drains 4.

The body 1 of the container 1 + 2 has in its upper part a shoulder 10. A gripping flange, useful for the handling of said body 1, is thus constituted.

The lid 2 of the container 1 + 2 has the shape of a dome 22 and has, in its upper part, a dome head 20. Of the same In this way, said dome head 20 constitutes a gripping means for handling said lid 2. On this lid 2, more precisely on its dome head 20, there is a degassing vent, not shown (question of scale).

Said cover 2 has been positioned and is temporarily stabilized on the body 1 thanks to the docking guide 3 (visible on the Figure 1B ), arranged in the upper internal part of said body 1, at its upper axial end 1 '(visible on the Figure 1B ).

The container thus pre-formed, temporarily closed in an unsealed manner, is intended to be introduced into an active cell 50 ( Figures 1B and 1C ), to be filled with nuclear waste and closed by a tight and mechanically resistant closure.

On the Figure 1B , it has been shown the step of removal (retraction) of the lid 2, which makes accessible the interior of the body 1 of the container 1 + 2. This removal of the cover 2 involves gripping means 6b of said cover 2, controlled by a bracket 6a, adapted to go up and down.

Said gripping means 6b of said lid 2 hold it while the body 1 is translated to a filling station (not shown). Once filled, the body 1 returns under the bracket 6a and is again capped with the cover 2. The docking guide 3 is still involved here for the docking of the two elements loaded body / cover (in other words for the guiding, laying said lid 2 on said body 1, loaded) and for stabilization, in contact with said body 1, said cover 2. The docking is thus implemented without pointing.

The loaded container, temporarily closed unsealed, is then translated to the welding station. Audit welding station - figure 1C - It intervenes another 6'a bracket, equipped with the welding machine with its centering device 6'b on the dome head 20 of the cover 2.

The welding takes place in a cornice position. The container 1 + 2 is fixed and it is the welding head 9 (plasma torch) which rotates around the joint to be welded J (contact area body 1 / cover 2). For a correct positioning of the elements to be soldered 1/2 (placed edge to edge, without spacing or chamfer), the stem 6'a descends so that the means 6'b rest on the dome head 20 of the cover 2. A compliance and ball joint system (not shown) makes it possible to make up for the positioning differences of the container 1 + 2 on the carriage 5 and to ensure precise centering . The support force is not negligible. It allows to keep in place, without play, the cover 2 and thus to exonerate any pointing before welding.

In order to overcome the variable distance differences, solder joint J / electrode, the welding head 9 is mounted on a motorized slide 8 driven automatically by the Arc Voltage Control (AVC); slide 8 itself mounted under an orbital plate 7.

Once the weld has been achieved, in at least one pass of the torch 9, the means 6'c (TIG torch, for example) are used to close off the expected degassing vent (not shown) on the dome head 20 of the cover 2. The presence of at least one such vent is essential to limit any internal overpressure in the container 1 + 2 during welding.

The docking cover 2 / body 1 could be implemented without pointing, thanks to the guide (to the ring) docking 3. Said guide 3 has also allowed the realization of a weld, continuous, penetrated, on the entire circumference of the accosted elements 2/1. The presence of a throat (see figures 2 , 2A, 2B, 2C and 3 following) in the structure of said guide 3 has in fact provided, on the one hand, the protection towards the weld and, on the other hand, the outlet of the plasma jet.

The loaded container, obtained at the end of the implementation of the welding, is thus closed, closed, in a sealed manner. The closure in question is also mechanically resistant. Said container, loaded, closed, is capable of being handled via the dome head 20 of its lid 2.

On the figure 2 , there is a container 1 + 2 of the invention, charged, closed, before closing the degassing vent 21, arranged in the dome head 20 of its lid 2. Said degassing vent 21 is likely to be clogged by welding, according to the TIG process mentioned above, without filler metal. It is in fact provided at the level of the structure of said vent 21, a reserve of sufficient material.

• en 1, le corps du conteneur 1+2. Ledit corps 1 est essentiellement cylindrique. Il présente un fond 11, une paroi axiale 12. Ladite paroi axiale 12 présente elle, en sa partie supérieure, un épaulement 10 et, au-delà dudit épaulement 10, son extrémité supérieure 12'. La soudure a été mise en oeuvre au niveau de cette extrémité supérieure 12' ;
• en 2, le couvercle du conteneur 1+2. Ledit couvercle comprend un dôme 22 surmonté d'une tête de dôme 20. En 23', on a l'extrémité inférieure dudit dôme 22, (plus précisément l'extrémité inférieure de la paroi verticale 23 dudit dôme 22) soudée à l'extrémité 12' de la paroi axiale 12 du corps 1 ; en 21, l'évent de dégazage, non encore obturé ;
• en 15, les déchets conditionnés dans le conteneur 1+2 ;
• en 3, le guide d'accostage, élément essentiel à la mise en oeuvre du centrage et du positionnement du couvercle 2 sur le corps 1 puis du soudage couvercle 2/corps 1.

On said figure 2 , we find, referenced:

• in 1, the body of the container 1 + 2. Said body 1 is essentially cylindrical. It has a bottom 11, an axial wall 12. Said axial wall 12 has it, in its upper part, a shoulder 10 and, beyond said shoulder 10, its upper end 12 '. The weld has been implemented at this upper end 12 ';
• in 2, the lid of the container 1 + 2. Said cover comprises a dome 22 surmounted by a dome head 20. At 23 ', there is the lower end of said dome 22, (more precisely the lower end of the vertical wall 23 of said dome 22) welded to the end. 12 'of the axial wall 12 of the body 1; in 21, the degassing vent, not yet closed;
• at 15, the waste packaged in the container 1 + 2;
• at 3, the docking guide, essential element in the implementation of the centering and positioning of the cover 2 on the body 1 and the welding lid 2 / body 1.

• son extrémité supérieure chanfreinée 3a se trouve, côté parois, au-delà du plan de soudure S et a donc contribué au guidage et positionnement du couvercle 2 lors de son accostage sur le corps 1 ;
• sa gorge 3b se trouve, côté parois, au niveau du plan de soudure S et a donc, lors de la mise en oeuvre du soudage, reçu le jet plasma traversant et assuré la protection envers de la soudure. Ladite gorge 3b est équipée d'au moins une cheminée de dégazage 3d. Elle est en fait équipée de quatre telles cheminées de dégazage 3d (voir la figure 3). La surpression générée dans ladite gorge 3 lors de la mise en oeuvre du soudage est évacuée successivement via lesdites cheminées de dégazage 3d et l'évent de dégazage 21 (figure 2).

It is now proposed to describe in greater detail said docking guide 3, with reference to the Figure 2A . On said Figure 2A it is clearly seen that the weld made S is a weld, edge to edge (end 12 'of the wall 12 of the body 1 / end 23' of the vertical wall 23 of the dome 22 of the cover 2), without filler metal . The docking guide 3, at issue on the Figures 1B , 2 and 2A , is an insert (as shown in perspective on the figure 3 ) welded punctually s to the internal structure of the upper part of the axial wall 12 of the body 1. It is welded in one direction and at an adequate level, so that:

• its chamfered upper end 3a is, on the wall side, beyond the weld plane S and has thus contributed to the guiding and positioning of the lid 2 during its docking on the body 1;
• its groove 3b is on the side of the walls, at the level of the weld plane S and therefore, during the implementation of welding, received the plasma jet through and provided protection against the weld. Said groove 3b is equipped with at least one 3d degassing chimney. It is actually equipped with four such degassing stacks 3d (see figure 3 ). The overpressure generated in said groove 3 during the implementation welding is successively evacuated via said degassing stacks 3d and the degassing vent 21 ( figure 2 ).

The docking guide 3 also has its chamfered upper end 3c, the inner side of the container. Advantageously, at this level the intervention of an internal cover which optimizes the confinement of the waste 15 in the container 1 + 2.

The docking guide 3 has also screened during the implementation of the welding. It protected the waste 15, in particular the temperature developed by the plasma jet.

• son extrémité inférieure chanfreinée 30a, côté parois, en deçà du plan de soudure S. Cette extrémité est parfaitement dimensionnée pour être en mesure d'exercer son action de guidage et de positionnement du couvercle 2, avant mise en oeuvre du soudage ;
• sa gorge 30b, côté parois, au niveau du plan de soudure S, équipée d'au moins une cheminée de dégazage 30d.

On the Figure 2B , the docking guide 30 is of the same type, insert, but said insert has been secured by welding, s, not to the body 1 of the container 1 + 2 but to its lid 2. Said docking guide 30 a :

• its lower end chamfered 30a, wall side, below the weld plane S. This end is perfectly dimensioned to be able to exert its guiding action and positioning the lid 2, before implementation of the welding;
• its groove 30b, side walls, at the weld plane S, equipped with at least one degassing chimney 30d.

Said docking guide 30 is not intended to receive an intermediate cover.

• 300a, son extrémité supérieure chanfreinée utile à l'accostage couvercle 2/corps 1,
• 300b, sa gorge utile au soudage,
• 300d, une cheminée de dégazage,
• 300c, son extrémité supérieure chanfreinée, côté intérieur, utile à la réception et la stabilisation d'un couvercle interne.

On the Figure 2C the docking guide 300 is not an insert. It is machined in the mass of the body 1. It has a shape quite similar to that of the guide 3 (of the Figure 2A ). We find in:

• 300a, its chamfered upper end useful for docking cover 2 / body 1,
• 300b, its groove useful for welding,
• 300d, a degassing chimney,
• 300c, chamfered upper end, inner side, useful for receiving and stabilizing an inner lid.

As stated above, the figure 3 shows in perspective the ring (guide) docking 3 of Figures 1B , 2 and 2A .

Claims (11)

1. A method of producing a closed container with a tight and mechanically strong seal by fastening two metal elements of the following type:

   a) a body (1) with an essentially cylindrical or prismatic shape having a base (11), one or more axial walls (12) and an open top axial end (1'); and

   b) a cover (2) the shape of which may be more or less complex, having one or more walls (23) to be positioned at the top axial end (1') of said body (1) facing the axial wall(s) (12) of said body (1) in the extension thereof;

   characterized in that it comprises the following two steps in succession, carried out in a hostile environment (50) in an automated manner, under remote control:

   - docking said two metal elements (1, 2) so that the ends (12', 23') of their facing walls (12, 23) are maintained in contact;

   - producing a continuous penetrative weld (S) over the entire periphery of said two metal elements (1, 2) at the ends (12', 23') of their walls (12, 23) which are maintained in contact.
2. The method according to claim 1, characterized in that said first docking step comprises a guided of said two elements (1, 2), a docking guide (3; 30; 300) being arranged in the internal structure of one of said two elements (1or 2).
3. The method according to claim 1 or claim 2, characterized in that said weld (S) is produced without spot welding, the ends (12', 23') of the walls (12, 23) of one or the other of said elements (1, 2) to be fastened being maintained in contact by exerting a force on one or the other of said elements (1 and/or 2), advantageously on the cover (2).
4. The method according to any one of claims 1 to 3, characterized in that said weld (S) is produced without a filler metal.
5. The method according to any one of claims 1 to 4, characterized in that said weld (S) is produced by open jet plasma process with melt-bath back cover and limiting the internal overpressure in the container produced.
6. The method according to claims 2 and 5, characterized in that said open jet opens intro a groove (3b; 30b; 300b) provided with at least one degassing chimney (3d; 30d; 300d) and machined in said docking guide (3; 30; 300) arranged in the internal structure of said body (1) or said cover (2); said body (1) and/or said cover (2), advantageously said cover (2), also being equipped with at least one degassing vent (21) which can be blanked off once said weld (S) has been produced.
7. The method according to any one of claims 1 to 6, characterized in that said weld (S) is produced with the container (1+2) in the vertical position, with the weld axis horizontal.
8. The method according to claim 7, characterized in that said weld (S) is produced with the container (1+2) being fixed and with a welding head (9) which is rotated around said container (1+2) at the level of the ends (12', 23') of the walls (12, 23) maintained in contact.
9. The method according to any one of claims 1 to 8, characterized in that it is carried out to produce a closed container for confined packaging and storage of hazardous waste, in particular nuclear waste.
10. A closed container with a tight and mechanically strong seal the structure of which comprises two metal elements of the following type fastened one with the other:

    a) a body (1) with an essentially cylindrical or prismatic shape having a base (11), one or more axial walls (12) and an open top axial end (1'); and

    b) a cover (2) with a more or less complex shape, having one or more walls (23) to be positioned at the top axial end (1') of said body (1) facing the axial wall(s) (12) of said body (1) in the extension thereof;

    characterized in that:

    the fastening is of the butt weld (S) type, advantageously with no filler metal;

    its internal structure at the weld line (S) includes a docking guide (3; 30; 300) which has:

    at the weld line (S), on the wall (12, 23) side, a groove (3b; 30b; 300b) provided with at least one degassing chimney (3d; 30d; 300d);

    a chamfered end (3a; 30a; 300a) above or below, preferably above said weld line (S), on the wall (12, 23) side;

    its body (1) and/or its cover (2), advantageously its cover (2), include(s) at least one blanked off degassing vent (21).
11. The container according to claim 10, characterized in that said docking guide (300) is machined in the bulk of the body (1) or the cover (2), advantageously machined in the bulk of the body (1), or consists of an insert (3; 30) spot welded to said body (1) or to said cover (2).

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